Bistable fluid logic element



April 4, 1967 w. F. voI'r, JR 3,312,244

' BISTABLE FLUID LOGIC ELEMENT Filed Dec. 24, 1964 FIG i I 2I 2? 22 I VALVED SOURCE SOURCEOFFLU'D vALvEDsoURcE 10 DF FLUID UNDER PRESSURE F FLUID UNDER PRESSURE UNDER PRESSURE FIQZ LI E I DURDE 2 SOURCE OFFLUID 21 VALVEDSOURCE 22 0F FLUID UNDER PREssURE UNDER PRESSURE UNDER PREssURE r v F 3 mm soURDE VALVED soURcE/ SOURCE OFFLUID vIILvED sDURcE f 0F FLUID 0F FLUID I UNDER PRESSURE 0F FLUID UNDER PREssURE UNDER PRESSURE UNDER PRESSURE I I I L l I 46 I (40 r 41///51p2 I 0 ss 36 HQ 4 SOURCEOFFLUIL/ g; HQ 5 soURcE 0F FLUID f UNDER PRESSURE 69/.UNDER PRE'DSURE UNDER PRESSURE VALVED SOURCE VALVED SOURCE OF FLUID 0F FLUID 0F FLUID INVENTOR. UNDER PRESSURE UNDER I3REssURE UND R PRESSURE WILLIAM F. Von, JR,

I ee 5 BY PUMP q),

ATTORNEY.

United States Patent "ice 3,312,244 BISTABLE FLUID LOGIC ELEMENT William F. Voit, .lr., Lexington, Ky., assiguor to International Business Machines Corporation, Armonk, N.Y., a corporation of New York Filed Dec. 24, 1964, Ser. No. 420,928 14 Claims. (Cl. 137-625.l8)

The present invention relates generally to the fluid and logic arts and more particularly to the provision of fluid elements each having a plurality'of stable states which are capable of performing various logic operations of the type usually accomplished by electrical components. 1

Recently, much interest has been evidenced in the possible use of various fluid operated elements to perform logical functions normally associated with electrical components. One such fluid element is the fluid jet amplifier wherein a stream of fluid issuing from an inlet nozzle is directed to either of a pair of outlet ports. The fluid jet is switched between the outlet ports by appropriately directed pressure gradients applied transversely across the fluid jet between the spaced nozzle and the pair of outlet ports. The pressure gradients are provided through the use of fluid control streams, vacuums, electrical discharges or the like. The fluid jet amplifier is a bistable device in that the fluid jet will remain directed toward a particular outlet port even though the controlling transverse gradient is removed due to the boundary layer condition existing between the fluid jet and the adjacent side wall of the outlet port.

Fluid elements of the type mentioned above are relatively fast acting, occupy a minimum of space and can be fabricated at a low cost employing conventional plastic molding techniques. The fluid elements can be interconnected to perform complex logic functions and are highly reliable in the sense they do not wear out and require replacement as do conventional electrical components. While these advantages have been widely recognized, several problems have somewhat limited the use of such fluid elements. A relatively large volume source of fluid under pressure is required since fluid is continuously moving through the fluid jet amplifiers and exhausted during standby conditions. Also, fluid jet amplifiers are load sensitive devices and various vents must be provided adjacent the outlet ports so that such amplifiers are not capable of performing much work.

Briefly, this invention is concerned with the provision of highly improved fluid logic elements each having at least two stable states. The basic fluid element comprises a thin strip or. tape of flexible material which is received in an elongated slot in a housing. Both ends of the tape are stationarily mounted or anchored with respect to the housing and an intermediate portion of the tape is free to move in the elongated slot. A pair of cavities are formed in the housing adjacent the slot and actuating ports communicate with the slot on the opposite side of the tape from the cavities. The tape is long enough and has suflicient slack so that it generally spans one of the cavities and is received in and conforms to the other of the cavities. A transversely extending pressure gradient is created by supplying fluid under pressure to the actuating port associated with the one of the cavities. The tape is very quickly element.

3,312,244 Patented Apr. 4, 1967 forced or deflected into the one cavity while at the same time being withdrawn from the other cavity. The material forming the tape, its dimensions and mounting, in combination with the dimensions and shapes of the cavities, are selected so that when the pressure gradient is removed the tape remains in its position with a portion of the tape received in the one cavity. To reset the tape, a transversely extending pressure gradient is created at the other cavity and the tape is deflected thereinto while being pulled from the one cavity.

The intermediate portion of the tape of the fluid element can be provided with properly positioned apertures that cooperate with inlet and outlet ports in the housing. Various pairs of inlet and outlet ports representing different conditions are in communication with each other or blocked depending on the stateo-f the fluid Tape elements can be designed and arranged to perform complicated logic functions, such as converting signals from one code to a different code or providing a tristable logic device.

It is the primary or ultimate object of the present invention to provide fluid elements each having a plurality of stable states and capable of performing logic functions. The fluid element comprises a thin strip or tape of flexible material which is movable longitudinally in a slot in a housing between two or more stable positions. At least two cavities are formed in the housing and the tape is deflected into a selected one of the cavities while being withdrawn from another of the cavities.

Another object of the invention is the provision of bistable fluid elements which can be combined with other generally similar fluid elements to perform complicated logic functions. Also, relatively low volume fluid supply means are required since the fluid elements are essentially fluid tight. Fluid, other than normal leakage, is not continuously exhausted during standby operations as in the case with conventional fluid jet amplifiers.

A further object of this invention is the provision of bistable fluid elements having the characteristics above described which are extremely simple in construction and operation. The elements are formed employing con-' ventional plastic molding techniques at low cost. The

fluid logic elements are highly reliable in operation and do not wear out as do analogous electrical components.

The foregoing and other objects and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention as illustrated in the accompanying drawings.

In the drawings:

FIGURE 1 is a side sectional view showing a bistable fluid element in one of its stable states constructed and operated in accordance with the teachings of the present invention;

FIGURE 2 is a side sectional view showing the bistable fluid element of FIGURE 1 in its other stable state;

FIGURE '3 is a side section-a1 view of a tristable fluid element employing the teachings of this invention;

FIGURE 4 is a side sectional view depicting another bistable fluid element of this invention in one of its stable states; and

FIGURE 5 is a side sectional view showing the bistable fluid element of FIGURE 4- in its other stable state.

Referring now to the drawings, and initially to FIG- URES 1 and 2 thereof, the reference numeral 10 designates generally a bistable fluid element embodying the teachings of the invention. The bistable fluid element comprises a housing 11 of plastic or other similar material which is formed with an opening to provide a generally thin and rectangular slot 12. Received within the slot '12 is a flexible rectangular strip or tape .13 of plastic or metal, such as Mylar or strip steel, for example. The tape 13 is anchored or attached to the housing 11 at both ends by bolts 14 and 15 or any other convenient attachment means.

Formed in the housing 11 adjacent the anchored ends of the tape and communicating with the slot 12 are a pair of generally U-shaped cavities 16 and 17. The bottoms of these cavities are exhausted to atmosphere by exhaust ports 18. Provided in the housing 11 on the opposite sides of the slot 12 and tape 13 from the actuating cavities 16 and 17 are actuating ports 19 and 20, respectively, which are in communication with valved sources of fluid under pressure schematically at 21 and 22 in the drawings.

The fluid element is assumed to be in one stable state when, as shown in FIGURE 1 of the drawings, the slack in the tape 13 is received within the cavity 16 and the tape span the other cavity 17. The length of the tape 13 is selected relative to the length of the slot and the configuraion of the cavities so that all slack in the tape is received vin one or the other of the cavities in accordance with the state of the fluid element. To switch the state of the fluid logic element, the valved source 22 of fluid under pressure is actuated, a force is exerted on the surface of tape 13 adjacent the actuating port 20 and a pressure gradient exists in a direction extending transversely of the tape. This pressure gradient immediately causes the tape to be deflected into and conform to the shape of the cavity 17 and pulled from cavity 16 as is clearly shown in FIG- URE 2 of the drawings. The cavities 16 and 17 each have approximately the same width dimension as that portion of the tape 13 adjacent the cavity so that fluid leakage is maintained at a minimum and does not markedly affect the speed of operation of the device. The intermediate portion 24 of the tape 13 between the cavities 16 and 17 moves through a linear distance corresponding directly to the slack in the tape. The exhaust ports 18 .prevent the entrapment of fluid and the buildup of fluid pressure between the bottom of the cavity 17 and the tape 13 so the tape moves very quickly and smoothly into the cavity. When the source of fluid under pressure 22 is effectively disconnected from the actuating port 20, the tape 13 remains in the condition shown in FIGURE 2 of thedrawings with the slack in the cavity 17. To reset the fluid element, a fluid pulse is supplied from valved source of fluid under pressure 21 to actuating port 19. The resulting transversely extending pressure gradient causes the tape 13 to conform to cavity 16 and be pulled from cavity 17 so that the bistable fluid element assumes its other stable state as shown in FIGURE 1 of the drawlngs.

The movement of the tape 13 into either of the cavities 16 and 17 is caused by a pressure gradient which extends transversely of the tape as explained above. It should be clearly understood that the pressure gradient can be created in various ways, including applying a fluid pulse to one side of the tape while exhausting the cavity as employed in connection with the illustrated embodiment of the invention. Alternately, fluid under pressure can be supplied continuously to the actuating ports while simultaneously opening one set of the exhaust ports and leaving the other set of the exhaust ports closed. A condition of pressure equilibrium exists in a cavity when fluid is supplied to the actuating port and the associated set of exhaust ports are blocked because of the nominal clearance between the edges of the tape and the cavity. Still another manner of providing the pressure gradient extending transversely of the tape to deflect the same into the cavity is to apply vacuum to a set of exhaust ports.

A highly important aspect of this invention is that the fluid element shown in FIGURES 1 and 2 of the drawings is a bistable device since it has a first stable state (the slack in the tape 13- received in cavity 16) and a second stable state (the slack in the tape 13 received in cavity 17). Experiments have shown that if the fluid element is properly designed and the tape correctly mounted, the tape will remain in either state after the fluid actuating signals are removed. The tape does not have sufficient energy stored in the deformed portion thereof to overcome the mass of the tape, the friction forces acting on the tape, the columnar strength of the tape and any other fluid [forces acting thereon when the intermediate portion of the tape is used as a valving element. The portion of the tape extending from the cavity in which the tape slack is received, across the other cavity and to the rigid mounting at the other end of the tape corresponds to and acts as a columnar beam. Very significant forces are required to initially buckle the resultant beam and the columnar strength of the tape is employed and relied upon in maintaining the tape in either stable state. In several successfully operating constructed embodiments of the invention, the tape employed was a piece of Mylar plastic having a thickness of one mil and a width of .312 of an inch. The cavities were each approximately .8 0 of an inch long and .165 of an inch deep at the deepest point.

Critical aspects of the design of the bistable fluid elements of this invention are the mounting of the tape and the thickness dimension thereof. It is recognized that if the tape is made'thick enough and/ or only one end portion of the tape is rigidly mounted or anchored to the housing, a monostable fluid element can be provided. Such devices are disclosed and more fully explained in my co-pending patent application Ser. No. 421,032, entitled Monostable Fluid Logic Element and Actuator, tiled concurrently with this application and assigned to the assignee of the present invention.

The bistable fluid element can be employed in a wide variety of logic applications. The intermediate portion 24 of the tape 13 is provided with a valving aperture 25. Also, the housing 11 has an inlet port 26 connected with a source of fluid under pressure 27 and an outlet port 28 leading to a fluid sensitive device, not particularly shown. When the fluid logic element is in its first stable state with the slack of the tape 13 in cavity 16, the valving aperture 25 in the intermediate portion 24 of the tape 13 is not aligned with inlet and outlet ports 26 and 28. These ports are effectively blocked and no fluid under pressure is directed to the fluid sensitive device connected to the outlet port 28. However, when the valved source of fluid under pressure 22 is actuated and the slack in the tape is forced into the cavity 17, the valving aperture 25 moves into alignment with inlet and outlet ports 26 and 28 as illustrated in FIGURE 2 of drawings. The valving aperture 25 preferably has a shape which permits the greatest fluid flow in the shortest length of tape, such as an elongated slot extending transversely across the Width of the tape. It is noted the fluid element of FIGURES 1 and 2 is essentially a memory element and the fluid source 27, inlet and outlet ports 26 and v28 and the fluid sensitive device may be employed to interrogate or sense the state, condition or information stored in this memory element.

It should be apparent that the use of the movable intermediate portion 24 of the tape as a valving member can take various forms. The valving aperture 25 can be positioned so the inlet and outlet ports 26 and 28 are in communication when the fluid element is in its first stable state. More than a single pair of inlet and outlet ports can be formed in the housing and more than one valving aperture can be provided in the intermediate portion of the tape as required to perform complicated valving functions, such as opening a plurality of fluid circuits while concurrently closing other fluid circuits; This makes the bistable fluid elements of the present invention particularly useful in performing logic operations in parallel since many fluid channels can be controlled by a single tape.

Another fluid element is shown in FIGURE 3 of the drawings. This device has three stable states and can be employed to perform more complicated logic functions. A housing 30 has a slot 31 therein which slidably receives a thin strip or tape 32 of strong flexible material. Both ends of the tape 32 are rigidly attached oranchored to the housing by bolts 33 and 34. The intermediate portion 35 of the tape is movable in the slot 31 and a pair of spaced valving apertures 36 and 37 are provided therein. Formed in the housing 30 adjacent the end of the tape anchored by bolt 33 are a pair of generally U-shaped actuating cavities 38 and 39. Actuating ports 40 and 41 are provided in the housing and are connected to individually actuatable valved sources of fluid under pressure 42 and 43, respectively. Also formed in the housing 30 adjacent the end of tape 32 anchored by bolt 34 is a resetting cavity 45 which produces a tape motion having a size at least equal to the combined tape motions provided by both of the actuating cavities 38 and 39. A reset port 46 is connected with valved source of fluid under pressure 47 so that the fluid element may be reset to its original stable state. Spaced pairs of inlet and outlet ports 49 and 50 are formed in the housing 30 and the inlet ports are connected to a source of fluid under pressure 51 while the outlet ports lead to pressure sensitive output devices, not shown.

If the unactuated and'stable state of the fluid elements as shown in FIGURE 3 of the drawings, all slack in the tape is received in resetting cavity 45 and the valving apertures 36 and 37 in the intermediate portion 35 of the tape are not aligned with the pairs of inlet and outlet ports 49 and 50. If fluid under pressure is applied to either of the actuating ports 49 or 41, the tape 32 is forced into the corresponding one of the actuating cavities 38 or 39 and is partially pulled from the resetting cavity 45. Under these conditions, the valving aperture 36 moves into alignment with the pair of ports 49 but the tape has not moved sufiicien-tly to cause aperture 37 to become aligned with the pair of inlet and outlet ports 50 and these ports remain blocked. This operation corresponds to the logical exclusive OR function in that either of two inputs, but not both, will provide a particular type of output. If at any time fluid under pressure is applied to both of the actuating ports 40 and 41 before resetting, the tape 32 is moved into both of the actuating cavities 38 and 39. The valving aperture 36 moves to the left past the pair of ports 49 while the valving aperture 37 moves into aligned relation with the pair of ports 50. This defines a second stable state which provides an output when all of a number of input signals are present and corresponds generally to the logical AND condition. I

The deflection of the tape into either actuating cavity 38 or actuating cavity 39 or into both of these actuating cavities defines two stable states of the fluid element. A third state is provided when valved source of fluid under pressure 47 is actuated to reset the tape and force the slack in the tape into resetting cavity 45 as shown in FIGURE 3 of the drawings. While two series related actuating cavities 38 and 39 have been described in connection with this embodiment of the invention, it should be understood that three or more actuating cavities can be employed depending on the results required for any given application. In this event, the resetting cavity would have a size to produce a tape motion at least equal to the combined tape motions caused by the actuating cavities. It is also possible to employ a plurality of actuating cavities of different sizes to perform various complicated logic functions, such as code conversion. This is the subject matter of and clearly explained in my co-pending patent application Ser. No. 429,929, entitled Fluid Display and Converter Device, filed concurrently with this application and assigned to the assignee of the present 6 invention. This co-pending patent application issued as Patent 3,263,922 on Aug. 2, 1966.

A slightly different form of bistable fluid element is shown in FIGURES 4 and 5 of the drawings. A blocklike housing 60 is formed with a pair inwardly facing crescent shaped actuating cavities 61 and 62. Actuating ports 63 and 64 are provided in the sides of the cavities 61 and 62 adjacent the inner walls thereof and are connected to valved sources of fluid under pressure 65 and 66, respectively. The bottoms of the crescent shaped actuating cavities 61 and 62 are joined by a horizontal slot 67 provided in the housing. A bore 68 extends through the center of the housing between the inwardly facing cavities 61 and 62 and is in communication with slot 67 to define a pair of inlet and outlet ports. A source of fluid under pressure 69 is connected with the inlet port provided by bore'63 while the outlet port is in communication with a fluid sensitive output device, not particularly shown. i

A thin flexible tape 70 is disposed in the actuating cavities 61 and 62 and the slot 67 connecting these cavities. The ends of the tape are anchored to the housing 64) by bolts 71 and 72 adjacent the upper corners of the crescent shaped cavities while an intermediate portion 73 of the tape is slidably received in the longitudinal slot 67. This intermediate portion 73 of the tape 70 has a valving aperture 74 therein which, in one state of the fluid element, is aligned with the inlet and outlet ports provided by bore 68. The tape 70 forms a movable fluid impervious diaphragm or wall in each of the crescent shaped cavities 61 and 62 and has a length or suflicient slack so that it is never pulled past the actuating ports 63 and 64 in a direction toward the inner facing walls of the cavities. If desired, the actuating ports may be formed in the innerfacing walls of the cavities to eliminate this requirement.

To actuate the fluid element and switch its state, fluid under pressure is applied to actuating port 63 while actuating port 64 is disconnected from its associated valved source of fluid under pressure 66. The pressure builds up between the inner wall of cavity 61 and the tape so that the tape moves outwardly until it conforms tothe v other and more complicated valving and logic functions can be accomplished by the provision of additional valving apertures in the movable portion of the tape and pairs of inlet and outlet ports in the housing. To return the bistable device to its original state, fluid under pressure is applied from source 66 to cavity 62.

It should now be apparent that the objects initially set forth have been accomplished. Of particular importance is the provision of fluid elements each having at least two stable states which are capable of performing various and complicated logic functions. The fluid elements are fast acting and characterized by their extreme simplicity in construction and operation. They can be manufactured at low cost using conventional plastic molding techniques and are relatively fluid tight.

While the invention has been particularly shown and described wtih reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. A fluid element comprising:

a housing having an elongated slot therein;

an elongated tape of flexible material movably received in said slot;

means for stationarily anchoring both ends of said tape relative to said housing;

atleast one actuating cavity formed in said housing adjacent said slot for receiving said tape; a source of input signals; output means carried by a movable portion of said tape spaced from said cavity; and means responsive to the input signals for creating a pressure gradient extending transversely of said tape for deflecting the same into said actuating cavity and causing movement of said tape in said slot to move said output means. 2. Apparatus according to claim 1 further characterized by:

said tape being relatively stifi' and resilient; and said tape, actuating cavity and slot being designed and formed of materials so that said tape remains in said actuating cavity when said transversely extending pressure gradient is removed.

3. Apparatus according to claim 2 further characterized by:

said output means comprising valving means carried by a movable portion of said tape;

conduit means for transferring energy disposed adjacent said movable portion of said tape; and

said valving means cooperating with said conduit means when said tape is in one of its positions.

4. Apparatus according to claim 2 further characterized by:

said output means comprises a valving aperture formed in a movable portion of said tape;

a pair of inlet and outlet ports formed in said housing opposite of said slot and communicating therewith; and

said valving aperture interconnecting said pair of inlet and outlet ports when said tape is in one of its positions.

5. Apparatus according to claim 2 further characterized by:

said source of input signals comprises a source of fluid under pressure; and

said means responsive to said input signals comprises an actuating port formed in said housing and communicating with said slot adjacent to and on the opposite side of said tape from said actuating cavity.

6. Apparatus according to claim 2 further characterized by:

said actuating cavity being U-shaped in cross sectional shape.

'7. A fluid element comprising:

a housing having an elongated slot therein;

an elongated tape of flexible material movably received in said slot;

means for stationarily anchoring both ends of said tape;

a pair of actuating cavities formed in said housing adjacent said tape for alternately receiving portions of said tape;

a source of fluid input signals;

means responsive to the fluid input signals for creating pressure gradients extending transversely of said tape for deflecting the same into said actuating cavities; and

said tape, actuating cavities and slot being designed and formed of materials so that said tape remains in one of said actuating cavities when said transversely extending pressure gradients are removed.

8. A fluid element comprising:

a housing having an elongated slot therein;

an elongated tape of flexible material movably received in said slot;

means for stationarily anchoring both ends of said tape relative to said housing;

a pair of actuating cavities formed in said housing and communicating with said slot;

a source of fluid input signals;

means responsive to said fluid input signals for creating fluid pressure gradients extending transversely of said tape for deflecting the same into said actuating cavities; p

said means responsive comprising an actuating ort for each of said actuating cavities formed in said housing and communicating with said slot adjacent to and on the opposite side of the tape from the associated actuating cavity;

valving means carried by a movable portion of said tape disposed between said actuating cavities;

conduit means for transferring energy disposed adjacent said movable portion of said tape; and

said valving means cooperating with said conduit means when said tape is in at least one of its positions.

9. Apparatus according to claim 8 further characterized by:

said valving means comprises a valving aperture in said movable portion of said tape spaced from said cavities; and

said conduit means comprises a pair of inlet and outlet ports .formed in said housing and communicating with said slot.

10. Apparatus according to claim 8 further characterized by:

said means responsive to said fluid input signals comprises an exhaust port communicating with the bottom of said actuating cavity.

11. Apparatus according to claim 8 further characterized by:

said tape being relatively stiff and resilient; and

said tape, actuating cavities and slot being designed and formed of materials so that the tape automatically remains in one of said actuating cavities when said transversely extending pressure gradient is removed.

12. A fluid element comprising:

a housing having an elongated slot therein;

an elongated tape of flexible material movably received in said slot;

means for stationarily anchoring at least a portion of said tape relative to said housing;

a plurality of actuating cavities formed in said housing disposed adjacent said slot for receiving portions of said tape;

a source of fluid input signals;

means responsive to the input signals for creating pressure gradients extending transversely of said tape for deflecting the same into selected ones of said actuating cavities and causing movement of said tape in said slot; and

said tape, actuating cavities and slot being designed and formed of material so that said tape remains in one of said actuating cavities when said pressure gradients are removed.

13. A fluid element comprising:

a housing having an elongated slot therein;

an elongated tape of flexible material movably received in said slot;

means for stationarily anchoring both ends of said tape relative to said housing;

a pair of actuating cavities formed in said housing adjacent said slot for receiving said tape; 7

said actuating cavities extending in angled relation relative to the longitudinal extent of said slot;

each of said actuating cavities having a pair of ends;

said slot interconnecting one set of ends of said actuating cavities;

said one set of ends being a given distance apart and said cavities being angled so that the other set of ends are substantially the same distance apart; output means carried by a movable portion of said tape spaced from said cavities; and means to deflect said tape into one of said actuating cavities while pulling the same from the other of d actuating cavities to move said output means.

9 10 14. Apparatus according to claim 13 further charac- References Cited by the Applicant i UNITED STATES PATENTS sa1d output means comprising valvrng means carried by the portion of said tape movable in said slot; 2,892,379 6/1959 Cooper. conduit means for transferring energy formed in said 5 2,904,070 9/1959 Lynott, housing between said cavities adjacent said movable 3,057,375 10/1962 Etter.

portion of said tape; and

said valving means cooperating with said conduit means M. CARY NELSON, Primary Examiner.

when said tape is received in a selected one of actu- I ti iti 10 R. C. MILLER, Assistant Examiner. 

1. A FLUID ELEMENT COMPRISING: A HOUSING HAVING AN ELONGATED SLOT THEREIN; AN ELONGATED TAPE OF FLEXIBLE MATERIAL MOVABLY RECEIVED IN SAID SLOT; MEANS FOR STATIONARILY ANCHORING BOTH ENDS OF SAID TAPE RELATIVE TO SAID HOUSING; AT LEAST ONE ACTUATING CAVITY FORMED IN SAID HOUSING ADJACENT SAID SLOT FOR RECEIVING SAID TAPE; A SOURCE OF INPUT SIGNALS; OUTPUT MEANS CARRIED BY A MOVABLE PORTION OF SAID TAPE SPACED FROM SAID CAVITY; AND MEANS RESPONSIVE TO THE INPUT SIGNALS FOR CREATING A PRESSURE GRADIENT EXTENDING TRANSVERSELY OF SAID TAPE FOR DEFLECTING THE SAME INTO SAID ACTUATING CAVITY AND CAUSING MOVEMENT OF SAID TAPE IN SAID SLOT TO MOVE SAID OUTPUT MEANS. 